The objectives of this proposed research are (1) to define the principle morphological changes observed during epidermal regeneration following abrasion, as well as to determine the changes in mitotic activity, amount of RNA, DNA and protein. (2) To determine the pattern of ribosome accumulation associated with the epidermal regeneration. Mice will have an area of epidermis removed from their backs by abrasion. Biopsy specimens will be taken daily to identify the principle morphological events as well as to determine the mitotic activity throughout the process of epidermal regeneration. At the same intervals homogenates will be prepared from trypsinized epidermis obtained from the regenerating epidermis, and the amount of RNA, DNA, protein, and nuclear count will be determined. Also at each interval of study of the above parameters, free and membrane bound ribosomes will be isolated.